The field of this invention is that of electronic circuit systems incorporating semiconductor devices and the invention relates more particularly to novel systems having improved means for reliably mounting semiconductor devices while also providing improved heat-dissipation from the devices.
This is a division of the commonly assigned, copending application, Ser. No. 260,970, of the same title of the present applicants filed Oct. 21, 1988. Related subject matter is disclosed in commonly assigned copending Patent Applications Ser. No. 166,300 entitled A COMPOSITE MATERIAL AND METHOD OF MAKING, now U.S. Pat. No. 4,885,214; Ser. No. 166,290 entitled A CIRCUIT SYSTEM, A COMPOSITE METAL MATERIAL FOR USE THEREIN, AND A METHOD FOR MAKING THE MATERIAL, now U.S. Pat. No. 4,894,293; and Ser. No. 247,799, entitled A MEMBER OF REFRACTORY METAL MATERIAL OF SELECTED SHAPE AND METHOD OF MAKING.
Semiconductor devices such as integrated circuit chips typically embody materials of relatively low thermal expansion properties so that when the devices are mounted on a substrate and when device terminals are electrically connected to circuit paths on the substrate to form a circuit system, it is difficult to maintain reliable mounting and electrical connection of the devices in the system while also effectively dissipating the heat generated in the devices during circuit operation. Where materials of high thermal conductivity have been employed to improve heat-dissipation, it has frequently been found that differences in thermal expansion between the semiconductor devices and such materials have tended to subject the device mountings and connections to thermal stress resulting in loss of mounting and connection reliability. On the other hand, where materials of low expansion properties have been employed to improve mounting and connection reliability, heat-dissipation from the devices has tended to be so restricted that the operating characteristics and service lives of the devices have been somewhat limited and the devices have been subject to parametric shifts. Many different substrate materials or mounting means have been proposed for improving heat-dissipation while maintaining suitable reliability but each has tended to be subject to deficiencies for some applications. For example, multilayer sheet materials embodying layers of metal of relatively low expansion properties metallurgically bonded to layers of metal of relatively high thermal conductivity are found suitable for use in many circuit substrates but are sometimes found to have heat-dissipation properties which are too limited for some applications. Some substrate materials embodying wire mesh or discrete elements of low expansion metal or the like disposed in a high thermal conductivity matrix of copper or aluminum have also been proposed for some applications but have tended to be relatively expensive to manufacture with the desired thermal conductivity properties. Other composite metal members adapted for mounting semiconductor devices have also been provided with selected shapes for improving heat-dissipation from the members. However, it would be desirable to provide novel heat-dissipating members, and circuits incorporating such members as well as materials for use in the members and novel methods for making the members and materials, to provide improved heat-dissipation and improved reliability of mounting and connection for semiconductor devices in such circuit systems.